At first glance the first part of the title confirms the inability of the second. HOWEVER we first need to understand why no one knows the day....because there is no day to know.
Why won't mankind know the day?
We need to further ask how is it possible for the Son of God not to know the day nor hour of timing of his own return being God himself?
Mark 13:32 But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father.
Alright, let start by looking at the events prior to Christ's return.
Re 6:12 And I beheld when he had opened the sixth seal, and, lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood;
Re 6:13 And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind.
Re 6:14 And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places.
Well we see some dramatic changes to this world. We see that just prior to Christ's return the sun is blackened, moon becomes as blood, and the stars fall from heaven and even heaven departing. How do we tell time? the sun, the moon, the stars. But what happens to these prior to Christ's return? lights out.
No one could possible know the day nor the hour because there will be no day no hour for the instruments to measure time have vanished.
The 1335 day count down
Da 12:11 And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days.
Da 12:12 Blessed is he that waiteth, and cometh to the thousand three hundred and five and thirty days.
So understanding that the reason which no one will know the day is that measured time has ceased (no matter if you have a watch you are measuring it to nothing)
God does gives us many signs pointing to his return even stating how many days in which Christ would appear. You just need to be on earth when the sacrifice and abomination is set up.
But I will tell you those who understand these signs won't last long.......